Current state-of-the-art navigation systems incorporate optical sensors, such as gyroscopes and optical accelerometers. These optical sensors include no moving parts and can sense rotations and accelerations with high bandwidth and high accuracy. For example, conventional laser gyroscopes utilize the properties of the optical oscillator, e.g., a laser, and the theory of relativity to produce an integrating rate gyroscope.
The laser gyroscope operates on a well-known principle that rotation of an operating ring laser, also referred to as an “optical oscillator”, about its axis causes the laser cavity to experience an apparent change in length for each direction. This apparent change in length creates a frequency shift in the laser oscillator in each direction. As between two counter-directionally travelling laser oscillations, portions of each may be superimposed so that the frequency shift is manifested as a beat frequency. This beat frequency is proportional to the rate of angular rotation of the gyroscope and is, therefore, measurable to provide an indication of the rate of angular rotation of the area circumscribed by the ring laser oscillator or ring laser gyroscope.
The laser gyroscopes offer high sensitivity, but there is a fundamental tradeoff between the size of an optical gyroscope and its sensitivity. The physical size of the gyroscopes which possess the requisite sensitivity for inertial navigation is acceptable for uses in commercial airliners or large nautical vessels. However, size, weight and power (SWaP) attributes are far more restricted in space launch vehicles, unmanned aerial vehicles, and other applications, so any reduction in size of the components of inertial measurement unit can yield major benefits or enable new applications.
Accordingly, there is a need to increase sensitivity of the optical sensors, such as optical gyroscopes and accelerometers, without increasing their SWaP attributes.